JPS5946311B2 - Method for preventing oxidation of heat-treated copper coatings - Google Patents

Description

[Detailed Description of the Invention] This invention provides a method for forming ceramic bodies such as dielectrics, insulators, resistors, and semiconductors by electroless plating, vacuum evaporation, sputtering, ion blating, etc.
The present invention relates to a method for preventing oxidation of a copper coating that has been subsequently heat-treated.

In general, methods for forming a copper film on the surface of a non-conductive material such as a ceramic body include electroless plating, vacuum evaporation, sputtering, and ion blating. It is known that it has uses such as when forming the electrode part of a ceramic capacitor.

The copper film formed by the above-described method is usually subjected to heat treatment after the film is formed in order to achieve densification, metallization, improvement of adhesion, and stabilization. This heat treatment is generally performed in an inert atmosphere to prevent the copper coating from reacting with oxygen. By subjecting it to this heat treatment process, the copper coating formed by electroless plating, vacuum evaporation, sputtering, ion blating, etc. becomes a copper coating with electrical properties close to those of pure copper. , constitutes a highly reliable electronic component. However, when copper coatings formed by electroless plating, vacuum evaporation, sputtering, etc. are subjected to a heat treatment process, they are more likely to oxidize than copper coatings that are not heat-treated.
It also becomes more susceptible to changes over time.

This is because the copper coating itself is a metal that is easily oxidized, and the high temperature heat treatment imparts catalytic activity to the surface of the copper coating, making it even more susceptible to oxidation. .

For this reason, if a heat-treated copper film is used as it is, for example, as an electrode for a capacitor, the conductivity will decrease due to the formation of an oxide film, and if it is left for a while after heat treatment, the solderability will also deteriorate, which is undesirable. A phenomenon was observed.

Therefore, the main purpose of this invention is to prevent oxidation and stabilize the surface of a heat-treated copper film, thereby
The object of the present invention is to enable long-term preservation of copper coatings and, in turn, increase the reliability of electronic components made of ceramic bodies on which copper coatings are formed.

That is, the gist of this invention is that after heat-treating a ceramic body with a copper coating formed on its surface, the surface of the ceramic body is treated with a volatile solvent such as trichlene, perchlorene, freon, or chlorobenzene in which a surfactant is dissolved. This method is characterized by contacting with a chargenated hydrocarbon compound solution.

Here, as volatile monologenated hydrocarbon compounds,
Examples include trichrene, perchrene, freon, and chlorobenzene, all of which have a boiling point of -29.8.
It is an existing substance with a low boiling point of ℃~132℃.

To explain the implementation outline of the method of this invention, first, thin film formation techniques such as electroless plating method, vacuum evaporation method, sputtering method, ion plating method, etc. to form a copper coating.

For example, a capacitor can be constructed by using dielectric ceramic as the ceramic body and forming a copper film on the surface, and alumina, zircon,
A circuit board can be constructed by using a ceramic substrate such as holsterite and forming a copper-coated circuit pattern on the surface.

In addition, various electronic components can be constructed by forming a copper coating on the surface of a ceramic element such as a resistor or a semiconductor. Various electronic components having copper coatings formed on the surfaces of ceramic bodies by various methods are then heat-treated at a temperature of, for example, about 700° C. in an inert atmosphere such as nitrogen.

The heat-treated copper film is metallized at this time, and its adhesion becomes strong, and its electrical properties are also improved, giving it very favorable properties.

However, because the copper coating undergoes a high-temperature thermal history through heat treatment, it is also given catalytic activity, resulting in a very active copper coating that has the same catalytic ability as Raney copper. Such catalytic activity can be obtained by contacting a solution of a volatile halogenated hydrocarbon compound such as tricrene, perchlorene, freon, or chlorobenzene in which a surfactant is dissolved as soon as possible after heat treatment.
Due to the poisoning effect of these volatile halogenated hydrocarbon compound solutions, the active sites in the copper coating disappear, catalytic activity disappears, and the copper coating becomes stable and less likely to be oxidized.

Furthermore, by forming a monomolecular film of a surfactant on the surface of the copper coating, oxidation and aging of the copper coating can be prevented. After the heat treatment, the time required for contacting the solution of a volatile monologenated hydrocarbon compound in which a surfactant is dissolved is preferably as short as possible, preferably within 30 minutes after the heat treatment. The surfactants used include, for example, anionic surfactants such as naphthenic soaps, cationic surfactants such as alkyloxazolines, nonionic surfactants such as polyethylene glycol esters, or amphoteric surfactants such as taurine fused succinates. activators, etc.
Any type of surfactant may be used as long as it dissolves in the volatile...logenated hydrocarbon compound solution, and the above-mentioned surfactants are not limited to the type.

Heat-treated copper coating and volatile surfactant
・The contact method with the logenated hydrocarbon compound solution is as follows:
There are methods such as applying, spraying, and dipping this solution, and any method may be used.

The present invention will be described below with reference to embodiments comprising electroless copper plating deposited coatings.

Example 1 A titanium oxide dielectric ceramic body having a diameter of 6.51 m1 and a thickness of 0.5 nm was immersed in an electroless copper plating solution to form a copper plating film on the entire surface of the ceramic body.

Next, this ceramic body was heated at 700°C in a nitrogen atmosphere.
After cooling, it was placed in a stainless steel net basket container and sprayed with trichlene in which 5% of polyethylene glycol ester having a molecular weight of 5,000 was dissolved. After that, the surface of the copper coating was naturally dried.

The ceramic dielectrics obtained in this way were left in a natural atmosphere for 24 hours, and the ceramic dielectrics were sprayed with trichloride in which a surfactant was dissolved and the ceramic dielectrics were not treated in this way. When the surface of the coating was observed, it was found that the coating that had not been treated by the method of the present invention began to take on a brown color and its solderability decreased.

However, with the method of this invention, no change was observed even after leaving it for one month, and the solderability was good. Example 2 Strontium titanate-based grain boundary insulated semiconductor porcelain with a diameter of 10.0 m, L, and thickness of 0.3 mm was prepared and immersed in an electroless copper plating solution to form a copper plating film on the entire surface of the semiconductor porcelain. .

Next, this semiconductor porcelain was placed in an inert atmosphere consisting of nitrogen.
Heat treatment was performed at 700°C.

Subsequently, the semiconductor porcelain on which the copper plating film was formed was immersed for about 1 minute in a Freon solution containing 5% naphthenic acid soap having a molecular weight of 5,000. The semiconductor porcelain was pulled out of this solution and air-dried to stabilize the copper plating film.

Furthermore, when this semiconductor porcelain was forcibly oxidized under the conditions of 95% humidity and 40° C., there was no change in color tone of the surface of the copper coating even after 5000 hours, and the solderability was also good.

As is clear from the above embodiments, according to the present invention, after heat-treating the surface of the copper coating of a ceramic body on which a copper coating is formed by electroless plating, trichlene or freon in which a surfactant is dissolved is applied. When brought into contact with a solution of a volatile halogenated hydrocarbon compound such as It is something.

In addition, in the above-described embodiment, an example of a copper coating formed by an electroless plating method was explained, but the same effect can be obtained even if the present invention is applied to a copper coating formed by a vacuum evaporation method, a sputtering method, or an ion plating method. Of course you can get it. Regarding ceramic bodies, we have explained dielectric ceramic bodies and grain-boundary insulated semiconductor porcelain, but this invention can also be applied to other materials made of dielectrics, insulators, semiconductors, and resistors with copper coatings formed on them. A similar effect can be obtained.

Claims (1)

[Scope of Claims] 1. A heat treatment characterized in that after heat-treating a ceramic body on which a copper coating is formed, the surface of the ceramic body is brought into contact with a volatile halogenated hydrocarbon compound solution in which a surfactant is dissolved. A method for preventing oxidation of copper coatings. 2. The heat-treated copper film according to claim 1, wherein the copper coating is formed by any one of electroless plating, vacuum evaporation, sputtering, and ion plating. Method for preventing oxidation of copper coatings. 3. The method for preventing oxidation of a heat-treated copper coating according to claim 1, wherein the ceramic body is any one of a dielectric, an insulator, a resistor, and a semiconductor. 4. The method for preventing oxidation of a heat-treated copper coating according to claim 1, wherein the ceramic body is a dielectric and the copper coating is an electrode for taking out a capacitance. 5. The method for preventing oxidation of a heat-treated copper coating according to claim 1, wherein the heat treatment of the ceramic body is performed in an inert atmosphere.